Matt’s Alice Springs Build

[Marvellous_Matt]

After talking about it for a few years we finally got around to starting a oven build. We had been gradually collecting Beser bricks and other building materials, and after having some paving laid though it was time to get into it.
As the fella doing the paving was pretty handy I elected to get his help. I’m not sure if that is not in keeping with the spirit of it, however as I thought it would take me at least 2 weekends to teach my self to lay blocks I payed the man and had it done in a morning!
So I dug some strip footings about 300 x 300, and it started to take shape.

[Marvellous_Matt]

The block work done.

[Marvellous_Matt]

I used some 6mm angle as a lintel, and I was going to lay the form ply straight on top, then put the hebel direct onto the formply. Well the big green shed sells hebel but not hebel cement, I could not work out if the alternatives would stick to the formply, so I ended up laying the hebel onto the top of the beser with tile cement, and liquid nails on the lintel. I then cut the form to fit inside, and cut holes for the core fill.

[Marvellous_Matt]

Core fill was pretty straight forward.
Slab was a working be, one mate helping and old mate who did the paving overseeing. Took about 2.5 hours.
I used concrete for the bottom of the slab (3:1) to cover the reo,then had 100l of vermiculite to add, so the top 90mm or so is 3:3:1. Pretty happy with the result, it is drying nicely.

[Marvellous_Matt]

We now have a little bit of time up our sleeve, have some firebricks on the way, should be here later this week however we plan to be away for the weekend so I have time to consider the next bit. I was had thought that next I would lay 50mm clay pavers as the base, full cover, and then build the dome out of half fire bricks directly on top of this. After finding this forum it looks like many people build them elevated on a further base.
Will the 90mm vermiculite mix have the right properties for the oven?

[david s]

The part of any WFO that takes the greatest beating is the floor. This is therefore the first place that firebricks should be used. Clay pavers for the floor may be suitable depending on their composition, but as they haven’t been designed for use in an oven or fireplace are unlikely to last. It is common for the floor bricks to be laid loose so they can be replaced, so if you want to go ahead with them i’d strongly recommend you do this. Generally but not exclusively, the lighter coloured pavers (lower iron oxide content) are more likely to be suitable.Your 90 mm vermicrete at 3:1:1 is really too dense to be a good insulator, but it is what it is now. The normal underfloor mix is 5:1 See attached link for insulation value of various mixes. Also the large amount of water required in a vermicrete mix leaves a lot of free water behind after the hydration process and it needs to be eliminated for the insulation to work properly. A good idea to allow it to dry before building over it. (See second attachment).

Vermicrete PHYSICAL PROPERTIES 2 copy.docx.zip

Vermicrete insulating slab copy.doc.zip